Yes I will be using it for a small incubator. Would top or bottom work better for it?Most ptc heaters can operate on either, like the types on the following page.
http://www.ihpheating.com/products/ptc-heaters/
Since yours specifically says AC and you're on 110, no worries.
Are you using it for an incubator?
I'm adding a small 12V ptc to get more heat at the bottom of the cabinet.